1. Field of the Invention
The present invention relates to a vibration isolation mount, and more particularly to a vibration isolation mount for supporting a transmission of a vehicle on a vehicle body in a vibration-isolated condition.
2. Description of the Related Art
Conventionally, a vibration isolation mount of this kind includes, for example, as shown in FIG. 15, a first platelike metal member 1, which is a rectangular metal plate, and a second platelike metal member 2, which is a rectangular metal plate. The first platelike metal member 1 is bent at substantially trisecting positions with respect to the longitudinal direction in such a manner that opposite end portions extend obliquely upward toward the same side and at the same angle. The second platelike metal member 2 is bent at longitudinally near-end positions at the same angle in such a manner as to be directed toward substantially the same directions as is the first platelike metal member 1. The second platelike metal member 2 is disposed substantially in parallel with the first platelike metal member 1 with a predetermined distance maintained therebetween. A pair of elastic rubber support members 3 are sandwiched between the first and second platelike metal members 1 and 2 so as to elastically connect the first and second platelike metal members 1 and 2. More specifically, each of the elastic rubber support members 3 is sandwiched between respective opposite bent portions of the first platelike metal member 1 and the second platelike metal member 2. A through-hole 1a is formed at the center of a horizontal portion of the first platelike metal member 1. An annular flange member 4 is coaxially fixed to the circumferential edge of the through-hole 1a. The annular flange member 4 slightly protrudes from the through-hole 1a upward and downward. A rubber covering portion 5 covers the flange member 4.
A small hole 2a is formed at the center of a horizontal portion of the second platelike metal member 2. A tubular metal member 6 is provided on the upper surface of the second platelike metal member 2 in such a manner as to stand around the small hole 2a. The tubular metal member 6 extends through the flange member 4, and the upper end of the tubular metal member 6 protrudes from the flange member 4. A metal stopper 6a is fixedly attached to the protruding end of the tubular metal member 6. The metal stopper 6a extends radially outward from the tubular metal member 6 and has a diameter slightly greater than that of the flange member 4. A bolt 7 is inserted into the tubular metal member 6 from the metal stopper 6a side such that its head is caught on the metal stopper 6a while its threaded end portion is screwed into a nut 8, which is fixedly attached to a central portion of the outer surface of the second platelike metal member 2. This vibration isolation mount is mounted on, for example, an FR (front engine rear drive) vehicle such that the first platelike metal member 1 is attached to a transmission section (or a vehicle body frame) and the second platelike metal member 2 is attached to the vehicle body frame (or the transmission section).
In the above-described vibration isolation mount, within a limited space provided between the elastic rubber support members 3, the flange member 4 is covered with the rubber covering portion 5. Through employment of this configuration, vertical vibrations input to the mount are damped by means of the elastic rubber support members 3 and the rubber covering portion 5, the rigidity of the mount in the front-and-rear direction is enhanced, and the rigidity of the mount in the right-and-left direction is appropriately adjusted, thereby improving riding comfort and enhancing steering stability.
The above-described vibration isolation mount requires a large number of metal component parts, including the first and second platelike metal members 1 and 2, the flange member 4, the tubular metal member 6, the metal stopper 6a, the bolt 7, and the nut 8. Additionally, a resin cap 9 for covering the nut 8 is required. Therefore, the cost of component parts is high. Also, welding must be performed for joining the first platelike metal member 1 and the flange member 4, the second platelike member 2 and the tubular metal member 6, the second platelike member 2 and the nut 8, and the tubular metal member 6 and the metal stopper 6a. Thus, the cost of welding is high. Furthermore, the elastic rubber support members 3 provided between the first and second platelike metal members 1 and 2 and the rubber covering portion 5 for Covering the flange member 4 must be formed through rubber vulcanization molding. Thus, the cost of pretreatment of the metal members for vulcanization molding and the cost of bonding agent are increased. Therefore, the cost of manufacturing the vibration isolation mount, including the cost of metal component parts, the cost of welding, and the cost of vulcanization molding, is high. Thus, reduction in the cost of the vibration isolation mount has been required.
Also, in the above-described vibration isolation mount, the first and second platelike metal members 1 and 2 assume an elongated structure such that bent portions extend in longitudinally opposite directions from a central portion. Therefore, the first and second platelike metal members 1 and 2 must assume an increased thickness in order to have a required strength, resulting in increase weight thereof. Also, being provided between bent portions of the first and second platelike metal members 1 and 2, the elastic rubber support members 3 are in an inclined position; thus, the elastic rubber support members 3 must be increased in thickness. As a result, the first and second platelike metal members 1 and 2 each resonate; i.e., have a resonance peak in a low frequency band, thereby generating dull sound.
An object of the present invention is to solve the above-mentioned problems in the conventional vibration isolation mount and to provide a vibration isolation mount which can be manufactured from a small number of component parts and according to a simple process without sacrifice of vibration-isolating performance, to thereby reduce cost.
To achieve the above object, the prevent invention provides a vibration isolation mount comprising a first platelike metal member assuming a rectangular shape, a first stopper member, a second platelike metal member, a second stopper member, a pair of elastic rubber support members, and an elastic rubber covering portion. The first stopper member comprises a pair of side plates, and a bottom plate. The side plates and the bottom plate are integrally formed into a shape resembling the letter U. End portions of the side plates are fixedly attached to one plane of the first platelike metal member at longitudinally opposite end portions so as to provide the first stopper member fixedly standing on the plane. The second platelike metal member is disposed a predetermined distance away from the first platelike metal member in a facing condition, with the first stopper member disposed therebetween. The second platelike metal member comprises a retaining portion provided at each of opposite ends thereof located in opposition to the opposite end portions of the first platelike metal member. The second stopper member is provided on the second platelike metal member at a longitudinally intermediate position in such a manner as to stand toward the first platelike metal member. An end portion of the second stopper member can be caught by the bottom plate of the first stopper member on the side toward the first platelike metal member so as to restrict the distance between the first platelike metal member and the second platelike metal member to a predetermined range. The paired elastic rubber support members are bonded to the plane of the first platelike metal member at the opposite end portions of the plane and extend toward the second platelike metal member. End portions of the elastic rubber support members are press-fitted in the corresponding retaining portions of the second platelike metal member so as to elastically connect the first and second platelike metal members. The elastic rubber covering portion is formed integrally with the elastic rubber support members and covers the surface of the bottom plate of the first stopper member.
The thus-configured vibration isolation mount of the present invention functions in the following manner. Main vibrations imposed vertically between the first and second platelike metal members are damped by means of the paired elastic rubber support members, which elastically connect the first and second platelike metal members. Furthermore, the paired elastic rubber support members enhance the rigidity of the vibration isolation mount with respect to the longitudinal direction of the mount (the right-and-left direction of vehicle) and allow appropriate adjustment of the rigidity of the vibration isolation mount with respect to the width direction of the mount (the front-and-rear direction of vehicle). Such control of vibrations in the front-and-rear and right-and-left directions improves riding comfort and enhances steering stability. Upon input of an excessive rebound in the vertical direction, an end portion of the second stopper member and the bottom plate of the first stopper member are caught by each other, thereby suppressing excessive tensile deformation of the elastic rubber support members in the vertical direction. Thus, the durability of the elastic rubber support members is ensured. Since the first and second stopper members are caught by each other, separation of the first and second platelike metal members is reliably prevented.
The present invention employs four metal members; specifically, the first platelike metal member, the second platelike metal member, the first stopper member, and the second stopper member, thereby considerably reducing the number of metal members as compared with the conventional vibration isolation mount. Also, since welding is only involved in joining the first platelike metal member and the first stopper member and in forming the second stopper member, assembly of the vibration isolation mount of the present invention involves less welding than does assembly of the conventional vibration isolation mount. Furthermore, vulcanization molding is collectively performed only once in forming a molding assembly of the first platelike metal member, the first stopper member, the elastic rubber support members, and the elastic rubber covering portion. Thus, vulcanization molding is performed fewer times and on fewer portions as compared with the case of manufacturing the conventional vibration isolation mount. Therefore, the cost of manufacturing the vibration isolation mount is considerably reduced.
According to the present invention, the elastic rubber support members are bonded to the first platelike member, and end portions of the elastic rubber support members are press-fitted in the corresponding retaining portions of the second platelike metal member; i.e., the elastic rubber support members are not bonded to the second platelike metal member. Thus, a molding assembly of the first platelike metal plate and the elastic rubber support members formed through vulcanization molding and bonding can be removed from a mold without involvement of demolding of the second platelike member of a complicated structure including the retaining portions. Therefore, the demolding structure of the mold can be simplified, and the molding assembly can be easily removed from the mold. Thus, the cost of mold is considerably reduced.
In the vibration isolation mount of the present invention, preferably, the second stopper member is formed in a U-like shape and disposed in such a manner as to surround the bottom plate. The second stopper member includes a pair of vertical plate portions standing on the second platelike metal member at a longitudinally intermediate position so as to sandwich the bottom plate of the first stopper member in a width direction thereof in such a manner that the vertical plate portions are separated from the bottom plate of the first stopper member, and a horizontal plate portion which connects the vertical plate portions.
Thus, upon input, to the vibration isolation mount, of an excessive rebound in the vertical direction, the horizontal plate portion of the second stopper member abuts the bottom plate of the first stopper member, thereby suppressing excessive deformation of the elastic rubber support members in the vertical direction. Also, since the first and second stopper members are caught by each other, separation of the first and second platelike metal members is reliably prevented. Upon input of excessive vibration component in the longitudinal direction, the horizontal plate portion of the second stopper member abuts the side plate of the first stopper member, thereby suppressing excessive deformation of the elastic rubber support members in the longitudinal direction. Upon input of excessive vibration component in the lateral direction, the vertical plate portion of the second stopper member abuts the bottom plate of the first stopper member, thereby suppressing excessive deformation of the elastic rubber support members in the lateral direction. Therefore, excessive tensile deformation of the elastic rubber support members in the vertical, right-and-left, and front-and-rear directions is suppressed, whereby the durability of the elastic rubber support members is ensured.
In the vibration isolation mount of the present invention, preferably, a through-hole is provided at the center of the bottom plate of the first stopper member, and the second stopper member comprises a vertical portion and a stopper plate. The vertical portion stands on the second platelike metal member at a longitudinally intermediate position and extends through the through-hole toward the first platelike metal member. The stopper plate is fixedly attached to an end of the vertical portion in such a manner as to be able to be caught by the bottom plate. Thus, upon input, to the vibration isolation mount, of an excessive rebound in the vertical direction, the stopper plate of the second stopper member abuts the bottom plate of the first stopper member at the periphery of the through-hole, thereby suppressing excessive deformation of the elastic rubber support members in the vertical direction. Also, since the first and second stopper members are caught by each other, separation of the first and second platelike metal members is reliably prevented. Upon input of excessive vibration component in the longitudinal direction, the vertical portion of the second stopper member abuts the bottom plate of the first stopper member at the wall of the through-hole, thereby suppressing excessive deformation of the elastic rubber support members in the longitudinal direction. Upon input of excessive vibration component in the lateral direction, the vertical portion of the second stopper member abuts the bottom plate of the first stopper member at the wall of the through-hole, thereby suppressing excessive deformation of the elastic rubber support members in the lateral direction. As a result, the durability of the elastic rubber support members is ensured.
In the vibration isolation mount of the present invention, preferably, the first platelike metal member and the second platelike metal member substantially assume the form of a flat plate, and the elastic rubber support members substantially assume the form of a rectangular parallelepiped block. Thus, the first stopper memberxe2x80x94which extrudes from the first platelike metal member toward the second platelike metal memberxe2x80x94and a second stopper memberxe2x80x94which stands on the second platelike metal member and whose end portion can be caught by the bottom plate of the first stopper member on the side toward the first platelike metal memberxe2x80x94constitute a rebound stopper structure. In contrast to the conventional vibration isolation mount, a stopper portion does not protrude outward from the first platelike metal member. Therefore, the vibration isolation mount of the present invention allows the first and second platelike metal members to substantially assume the form of a simple, flat plate. In the vibration isolation mount, since a pair of side plates of the first stopper member are fixedly attached to longitudinally opposite end portions of the first platelike metal member, the rigidity of the first platelike metal member is enhanced. Therefore, even when the first platelike metal member is formed into the shape of a flat plate, its thickness can be reduced. Also, since the first platelike metal member is formed into the shape of a flat plate, the second platelike metal member can be formed into the shape of a flat plate, so that the thickness of the second platelike metal member can be reduced. Thus, since the first and second platelike metal members can be reduced in thickness, the weight of the vibration isolation mount is reduced.
In the vibration isolation mount of the present invention, since the first and second platelike metal members assume the form of a flat plate, the elastic rubber support members can substantially assume the form of a rectangular parallelepiped block which is not inclined with respect to the axial direction. Substantially assuming the form of a rectangular parallelepiped block, the elastic rubber support members exhibit enhanced rigidity with respect to the vertical direction of a vehicle. Therefore, as compared with the conventional vibration isolation mount, the elastic rubber support members can be reduced in wall thickness as measured along the longitudinal direction of the vibration isolation mount, whereby the spring constant of the vibration isolation mount can be reduced with respect to the longitudinal and lateral directions. Furthermore, as a result of impartment of the form of a flat plate to the first and second platelike metal members, the resonance frequency of the first and second platelike metal members can be shifted toward high-frequency side, thereby avoiding generation of dull sound of a low frequency band which is observed in the conventional vibration isolation mount.
In the vibration isolation mount of the present invention, preferably, the retaining portions of the second platelike metal member comprise a pair of first engagement portions, two pairs of second engagement portions, and a pair of recess portions. The paired first engagement portions stand toward the first platelike metal member at the corresponding longitudinal ends of the second platelike metal member. Each pair of second engagement portions stands toward the first platelike metal member at laterally opposite ends of the second platelike metal member and in the vicinity of the corresponding longitudinal end of the second platelike metal member. Each of the paired recess portions is provided between the corresponding first engagement portion and the corresponding paired second engagement portions. Thus, end portions of the elastic rubber support members are press-fitted in the corresponding retaining portions of the second platelike metal member in such a manner as to be press-fitted in the corresponding recess portions while being compressed through abutment with the paired first engagement portions standing at longitudinally opposite ends of the second platelike metal member and abutment with two pairs of second engagement portions, each pair standing at the laterally opposite ends of the second platelike metal member and in the vicinity of the corresponding longitudinal end of the second platelike metal member. Thus, the elastic rubber support members are firmly fitted in the corresponding retaining portions. As a result, the elastic rubber support members appropriately exhibit vibration-isolating characteristics.
In the vibration isolation mount of the present invention, preferably, the first engagement portions and/or the second engagement portions are bent toward the corresponding recess portions of the second platelike metal member in such a manner as to overhang the recess portions. Being bent toward the recess portions, each of the first engagement portions and/or the second engagement portions assumes an inlet-narrowed pocket-like structure. Thus, end portions of the elastic rubber support members are press-fitted in the retaining portions of the second platelike metal member while being firmly caught in such pocket portions. Therefore, the elastic rubber support members are more firmly fitted in the corresponding retaining portions.
In the vibration isolation mount of the present invention, preferably, the first engagement portions and/or the second engagement portions are bent toward the corresponding recess portions of the second platelike metal member in such a manner as to overhang the recess portions, and end parts of the first engagement portions and/or end parts of the second engagement portions are bent away from the corresponding recess portions. Being bent away from the recess portions, the end parts serve as guides, so that end portions of the elastic rubber support members can be smoothly fitted into the retaining portions.
In the vibration isolation mount of the present invention, preferably, in place of the first engagement portions, a first linear protrusion is provided in each of the recess portions of the second platelike metal member at a longitudinally intermediate position in such a manner as to protrude toward the same side as do the second engagement portions and to extend in the lateral direction, or in place of the second engagement portions, a second linear protrusion is provided in each of the recess portions of the second platelike metal member at a laterally intermediate position in such a manner as to protrude toward the same side as do the first engagement portions and to extend in the longitudinal direction; furthermore, an engagement groove is formed on each of end portions of the elastic rubber support members so as to be engaged with the first protrusion or the second protrusion. Engagement of the first linear protrusions of the second platelike metal member with the corresponding engagement grooves on the elastic rubber support members prevents longitudinal movement of the elastic rubber support members as in the case where the first engagement portions are provided. Alternatively, engagement of the second linear protrusions of the second platelike metal member with the corresponding engagement grooves on the elastic rubber support members prevents lateral movement of the elastic rubber support members as in the case where the second engagement portions are provided.
In the vibration isolation mount of the present invention, preferably, end portions of the elastic rubber support members to be press-fitted into the corresponding retaining portions comprise positioning protrusions protruding to the outside of the retaining portions through cutout portions provided between the first and second engagement portions so as to be caught on the first and second engagement portions. Being caught on the first and second engagement portions, the positioning protrusions reliably prevent longitudinal and lateral movement of the end portions of the elastic rubber support members in the vibration isolation mount.